A receiving unit as generally described above is disclosed, for example, in English Pat. No. A1-41261. In the solution described there the push-in frame is swung out of the front plate of the apparatus into its input/output position, so that an input/output slot for inserting or removing the card is unblocked. In the operating position, on the contrary, the push-in frame is swung in in such a way that its one side is fully aligned with the front plate of the apparatus and the input/output slot is covered. For fixing the push-in frame in its operating position a relatively complicated mechanical locking mechanism is used which can be released from the outside by pressure on a button so that the push-in frame is conveyed into its input/output position under the action of a prestressing spring.